Cleaning and preserving of metallic surfaces



252. COMPOSITIONS,

Patented June 2, 1931" UNITED STATES lz'ximt PATENT OFFICE THOMAS W. BARTRAM AND DEAL H. TOMPKINS, OF NITRO, WEST VIRGINIA, ASSIGNORS TO THE RUBBER SERVICE LABORATORIES COMPANY, OF AKRON, OHIO, A COR- PORATION OF OHIO CLEANING AND PRESERVING OF METALLIC SURFACES No Drawing. Application filed March 20, 1980,

The present invention relates to the cleaning and preservation of metalllc surfaces, wherein the surface is in contact wlth a liquid of an acid nature. More particularly, the invention relates to the prevention of excessive pitting and embrittlement of a metal when subjected to a pickling process. The invention includes the provision of a regulator or inhibitor for causing the acid solution selectively to attack unclean portions of a metallic surface immersed therein to the substantial exclusion of any corrosive action upon clean portions of the metal surface.

Certain objects of the invent-ion are to prevent the pickle liquor from attacking ean portions of the surface of a metal; to ob iate over pickling, embrittlement and pittlng of the articles treated; to minimize the amount of metal lost in pickling; to increase the efliciency of the pickling operation and to prolong the effective life of the pickling bath and particularly to speed the pickling operation. Other and further objects of the invention will be apparent from the following description and accompanying examples.

In the art of pickling, the metal is treated with a dilute acid to remove oxides such as rust. scale and other deposits, after which the metal is preferably washed with Water and dipped into an alkaline bath to remove the last traces of free acid. The acid removes the rust and scale. but unfortunately, from the pickling standpoint, it attacks the cleaned metal itself thereby causing loss of metal and producing an evolution of hydrogen gas, which escapes into the air carrying with it a fine spray of the pickling bath and producing an atmosphere possessing corrosive properties and one which is highly injurious to health.

By the present invention, these objectionable features of the pickling process are substantially overcome. To accomplish this in accordance with the present invention, there is added to the pickling bath a regulating agent or ingredient which acts to restrain the action of the acid attacking clean metal but assists removing the rust, scale and other depositsror in other words it selectively re- Serial No. 437,597. Renewed December 4, 1930.

moves said materials without materially attacking the free metal.

The regulator or inhibitor, as dlsclosed in the present application, comprises a sul fonaged aldehyde-amine reaction product and pref rainy a 'sulfonated 'aldehyde derivative of a Schifis base; that is, a product formed by reacting an aldehyde with a Schiffs base, and further treating the product so formed with sulfuric acid of any concentration necessary to produce sulfonation at the reaction temperature employed.

In the examples hereinafter set forth for carrying out the metal pickling process, conditions were imposed which duplicated, so far as possible, those commonly followed in commercial practice, so far as concerned acid concentrations and temperatures employed.

Test pieces of steel approximately 4" x 1 x 4; in dimension were cut from a sheet of steel known to the steel trade as S. A. E. 1020. These pieces were then immersed in approximately 500 cc. of a water solution of sulfuric acid containing approximately 8% by weight of 66 B. acid to which had been added a small quantity of one of the preferred type of inhibitors. The quantity of hydrogen evolved by the action of the acid on the metal test strip was then collected over a definite period of time and the quantity was determined by measurement. The temperature of the pickling bath was maintained at from 176 to 185 F. (80 to 85 (3.). For the acid concentration set forth, commercial practice is to pickle at approximately 150 to 190 F. (66 to 88 C.) The results so obtained were compared with similar tests wherein the steel pieces were subjected, under the conditions set forth, to the action of an acid solution of the strength specified above but containing no inhibitor. Comparison of the quantity of gas evolved, which, as is well known is proporof strong sulfuric acid and the product formed from the reaction of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline, according to the method set forth in U. S. Patent No. 1,659,152 granted to Clayton Olin North, were reacted preferably by placing the aldehyde-amine product in a suitable vessel and adding sulfuric acid having a specific gravity of substantially 1,834, slowly thereto. Considerable heat was evolved during the addition of the sulfuric acid to the aldehyde-amine product and the temperature of the reacting mass quickly rose to approximately 160 C. The product resulting from this reaction after cooling, was a hard solid, which formed a fine powder when ground that was readily soluble in a pickle liquor as for example dilute sulfuric acid or dilute hydrochloric acid. A sample of the material prepared or described was incorporated in a. pickling bath in the manner hereinbefore described. The following table sets forth a comparison between the quantityof hydrogen evolved (which is a direct measure of the action of the pickle liquor on the steel test pieces) when the preferred inhibitor was employed and when no inhibitor was employed.

The results given in Table I show that the quantity of hydrogen generated and therefore the loss in weight of the test piece is very much less than that resulting under similar conditions when no inhibitor is present in the pickling acid. As the results clearly show, the loss in weight when no inhibitor is employed is approximately fifteen times greater than the loss resulting when the iiihibitor set forth is employed in the pickle bath. A greater saving in metal losses results from the use of a larger amount of the inhibitor.

As further examples of the preferred type of inhibitor, a sulfonated aldehyde-amine reaction product has been prepared by reacting other than equi-Inolecular proportions of an aldehyde-amine product and sulfuric acid of sufiicient concentration to produce sulfonation, but preferably sulfuric acid having a specific gravity of 1.834. Thus, the reactionproduct of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline has been sulfonated in a manner substantially as described by" reacting it with concentrated sulfuric acid in the ratio of substantially one molecular proportion of the aldehyde-amine reaction product to substantially 0.5, 0.8 and 1.1 molecular proportions of concentrated sulfuric acid. The sulfonated products thus formed were tested in the manner hereinbefore set forth and found to comprise very desirable inhibitors. The results of tests showing the inhibiting characteristics of these materials is set forth in Table II.

Table II Molecular proportions Amt of cc. of Inhibiting (Immpiound emof H1 80:i inhibitor Hydro- Trims,

p oye emp oye gen genruinu es in preemployed erated paring inhibitor Sulfonated reaction product of substantially three molecular proportions of acetaldebyde and substantially two molecular g. proportions of aniline..- 0.5 0.215 300 175 Do 0.8 0.235 300 185 Do 1.1 0.25 300 185 None 300 12.5

In the above table the quantities of sulfonated aldehyde-amine employed are based on the aldehyde-amine content of the respective products and are substantially molecularly equivalent to one another.

It is evident from the data set forth in Table II that the preferred inhibiting properties of the class of products set forth are exhibited by sulfonated aldehyde-amine products obtained by the use of varying proportions of the sulfonating agent.

Other sulfonated aldehyde-amine reac tion products and preferably sulfonated aldehyde derivatives of Schiifs bases have been prepared in a manner analogous to that here, inbefore set forth and tested as inhibitors in a pickling bath in the manner described. Thus methylene..dipineridinennhvd ofo naldehyde-aniline, the aldehyde .deriv-ativeof aSchiifs-basdffifid by reacting substantially three molecular proportions of butylaldehyde with substantially one molecular proportion of aniline, thewmaflilionlproduct of diphenyl guanidine.andioxmaldehyde, the

aldehyde and ethyl amine and of croton aldehyde-aniline among others have been reacted with sulfuric acid in the manner described and the s'ulfonated products employed in a pickling bath and tested in the 252. COMPOSITIONS,

Table III Amount of inhibltor employed cc. of Hydrogen generated Time requ red in minutes Inhibiting compound employed Sullonated methylene dipiperidine. Sulfonated anhydrol'ormaldehydeaniline Sulfonated reaction product of substantially three molecular proportions of butylaldehyde and substantially one molecular proportion of aniline Sulfonated reaction product 01 diphenyl guanidine and formaldehyde Sulfonated reaction product of diphanyl guanidine and metaldehyde Sulfonated formaldehyde derivative of the reaction product of substantially three molecular proportions of acetaldehyde and substantially ltwo molecular proportions of aniiue Sulfonated reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of otoluidine Sulfonated reaction product of ethylamine and formaldehyde Sulfonated reaction product of crotonaldehyde-anlline None In the above table the quantity of sulfonated aldehyde-amine employed is based on the weight of aldehyde-amine used in their preparation. In the first two examples given this is 0.1 g. and in the last seven examples this is 0.2 g. of aldehyde-amine.

It is thus apparent fro-m the data set forth that the preferred class of materials constitute an important group of inhibitors, as in all cases where one of the preferred inhibiting compounds was incorporated in the pickle liquor there was much less of hydrogen evolved in a given period of time and therefore a correspondingly less loss in weight in the steel test strips than was the case where no inhibitor was employed.

The preferred class of inhibiting compounds has also been employed in other pickling baths than sulfuric acid wherein materials other than iron and steel were pickled. The following example illustrates one method of pickling a nickel chromium alloy, wherein one of the preferred inhibitors, for example, the product formed by sulfonating the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline was employed as an inhibitor in a hydrochloric acid pickling bath.

A piece of nickel chromium alloy wire having a composition of nickel and 20% chromium, 36 feet in length, 0.036 inches in diameter, having a total surface of 4.07 square inches and weighing 5.1855 g. was coiled in the form of a spiral and immersed in approximately 500 cc. of 18% hydrochloric acid containing 0.18 g. of the sulfo- Emmi nated reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline. After allowing the wire to remain 'in the pickle liquor for 40 minutes at 180 F.

the loss in weight was found to be only 0.006 g. per square inch of surface exposed. A test identical with that described with the exception that the nickel-chromium wire weighed 5.1846 g. and no inhibitor was employed showed a loss of 0.058 g. per square inch of surface exposed. In other words, the weight loss due to solvent action of the acid on the metal was only as great when the inhibitor was employed as was the loss with no inhibitor present.

Furthermore, it has been found that, if convenient or desirable, the preferred class of inhibiting compounds ma be em 1 'n i wwhim riomzabl stance, for exam le sodium chlgride, sodium aceta e an 6 l1 (e whereupon the inhibiting properties of the products described are materially increased.

lVhat is claimed is:

1. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a sulfonated aldehyde-amine reaction product.

2. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a sulfonated aliphatic aldehyde-aromatic amine reaction product.

3. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution to which is added a small portion of a sulfonated aldehyde derivative of a Schiffs base.

4. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution to which is added a small proportion of a sulfonated reaction product of an aliphatic aldehyde containing less than five carbon atoms and a primary amine.

5. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution to which is added a small proportion of a sulfonated reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular and the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline at substantially 155 to 165 C.

7. A pickling bath for iron and steel products comprising a sulfuric acid solution of a sulfonated aldehyde-amine reaction product.

8. A pickling bath for iron and steel products comprising a sulfuric acid solution of a sulfonated aliphatic aldehyde-aron'iatic amine reaction product.

9. A pickling bath for iron and steel products comprising a sulfuric acid solution of a 1sjulfonated aldehyde derivative of a Schitts ase.

10. A pickling bath for iron and steel products comprising a sulfuric acid solution of a sulfonated reaction product of an aliphatic aldehyde containing less than five carbon atoms and a primary amine.

11'. A pickling bath for iron and steel products which comprises a sulfuric acid solution of a sulfonated reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline.

12. A pickling bath for iron and steel products which comprises a sulfuric acid solution of a product formed by heating substantially equi-molecular proportions of concentrated sulfuric acid and the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline at substantially 155 to 13. A process of pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution containing a small proportion of a sulfonated aldehyde-amine prodnot.

14. A process of pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution containing a small proportion of a sulfonated aliphatic aldehydearomatic amine reaction product.

15. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a sulfonated aldehyde-amine product.

16. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a sulfonated aliphatic aldehyde-aromatic amine reaction product.

In testimony whereof we hereunto afiiX our signatures.

THOMAS W. BARTR-AM. DEAL H. TOMPKINS. 

